Image icon  Thin section of ZnO varistor

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Description: The micrograph shows structure of ZnO, containing small amounts of oxides such as Sb2O3 and Bi2O3. Thin section was produced using liquid phase sintering: gives rise to a structure consisting of conductive ZnO grains with the additional oxides being preferentially located at grain boundaries. A varistor is used to short-circuit transient high voltage spikes in electronic devices. Incorporated into circuits, in parallel with the device to be protected. Acts as an insulator below a certain breakdown voltage, but as a conductor at higher voltages, due to highly non-linear I-V relationship.
Keywords: ceramic • oxygen • varistor • zinc
Categories: Science approaches > Microstructure
Materials > Ceramics & glasses > Technical ceramics
Applications > Electronics
Properties > Electrical, magnetic & optical > Conductivity
Testing, analysis & experimentation > Metallography
Scale > Micro
Created by: Dr K M Knowles, Department of Materials Science and Metallurgy, University of Cambridge
DoITPoMS, University of Cambridge
Published by: DoITPoMS, University of Cambridge
License: This resource is released under the Creative Commons Attribution Non-Commercial Share Alike license (2.0 UK: England & Wales).
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Date created: 09 August 2002
Date added: 21 August 2009
Resource ID: 1208